Abstract

Sewage sludges are routinely applied to agricultural soils in many countries. There are potential benefits to agriculture in terms of improved soil structure and nutrient additions, but there is a need to safeguard against possible unwanted environmental effects from heavy metals and trace organic contaminants added to soil in this form. Regulations have been enforced to restrict the additions of metals in sludge, but much less information exists to support scientifically-based restrictions for trace organics. Chlorobenzenes (CBs) are always present in sludges and possess a range of properties which suggests that soil-borne CBs may be susceptible to transfer to crops, grazing livestock and groundwater. In the absence of data specific to sludge amended soils and prior to a detailed case study of these compounds in sludge treated soils, this paper presents a review of the potential behaviour and fate of CBs in soil-plant systems. Volatilisation is identified as an important fate of CBs in soil, while degradation is thought to be minor. Plant uptake is deemed likely to occur, with the potential for transfer to root and shoots. This group of compounds provide a useful insight into the likely behaviour of other non-polar trace organics which may be present in sewage sludges.